You can experiment on this approach. I don't see anything too special or too risky with this betting method. The level of risk depends on how much money your starting bet is considering that you intend to do a Martingale. Just make sure you still have enough bankroll in the unlikely event that you lose for 4 consecutive matches. If you start with $20 on Barcelona, for example, you have to prepare $620 for a Martingale up to 5 in a row.

But take note that Martingale on sports betting may not work like Martingale on dice, for example, because of odds. To a certain extent, therefore, Martingale on sports betting doesn't serve its original purpose. Martingale is supposed to be a strategy which allows you to recover all your previous losses and even make a profit as if you won in your first bet.

If you apply this on sports betting, say, you place a $20-bet on Barcelona and you lose. You double on your next bet and you win. It doesn't mean you recovered your $20 loss. It may happen that you won on a 1.20 bet, meaning you only won $8 from your $40 bet, which further means you still have a net loss of $12.